<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

        * {
            padding: 0px;
            margin: 0px;
            list-style: none;
        }

        .ul>li {
            line-height: 30px;
            height: 30px;
            vertical-align: middle;
        }

        /* 伪元素必须要用contnet属性，即使为"" */
        /* 大部分情况，需要使用display改为块级或者行内块，默认情况是inline */
        .ul>li::before{
            content: "";
            display: inline-block;
            width: 20px;
            height: 20px;
            background-color: #ff0000;
            border-radius: 50%;
            vertical-align: middle;
        }

        .ul>li::after {
            content: "";
            display: inline-block;
            width: 20px;
            height: 20px;
            background-color: #00ff00;
            vertical-align: middle;
            transform: rotate(45deg);
        }


    </style>
</head>
<body>
    <ul class="ul">
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
        <li>7</li>
        <li>8</li>
        <li>9</li>
        <li>10</li>
    </ul>
</body>
</html>